function [A]=AarrayBuild(F_f_c,V,delta_t,c_s_)
%建立A矩阵
global mu num d b S_p own U_inlet c_s f_c V_c F_f
A_1=eye(num)/delta_t;
Ap=A_1+kron((F_f_c*ones(num,1)/2+mu*(c_s_.*d)*ones(num,1))./V,ones(1,num)).*eye(num);
An=F_f_c/2-mu*(c_s_.*d);
An=An./kron(V,ones(1,num));
A=Ap+An;
%引入速度边界条件
for i=1:b.in(1)
    l=own(i+b.in(2));%边界面对应单元的编号
    s_b=sqrt(c_s(i+b.in(2)-1,:)*c_s(i+b.in(2)-1,:)');%边界面的面积
    d_b=sqrt(sum((V_c(l,:)-f_c(i+b.in(2)-1,:)).^2));%边界单元到边界的距离
    U=U_inlet;
    S_=mu*s_b*U/d_b-F_f(i+b.in(2)-1)*U;
    S_p(l,:)=S_p(l,:)+S_/V(l);
    A(l,l)=A(l,l)+mu*s_b/d_b/V(l);
end
for i=1:b.cylinder(1)
    l=own(i+b.cylinder(2));%边界面对应单元的编号
    s_b=sqrt(c_s(i+b.cylinder(2)-1,:)*c_s(i+b.cylinder(2)-1,:)');%边界面的面积
    d_b=sqrt(sum((V_c(l,:)-f_c(i+b.cylinder(2)-1,:)).^2));%边界单元到边界的距离
    U=0;
    S_=mu*s_b*U/d_b-F_f(i+b.cylinder(2)-1)*U;
    S_p(l,:)=S_p(l,:)+S_/V(l);
    A(l,l)=A(l,l)+mu*s_b/d_b/V(l);
end
for i=1:b.sym1(1)
    l=own(i+b.sym1(2));%边界面对应单元的编号
    A(l,l)=A(l,l)+F_f(i+b.sym1(2)-1)/V(l);
end
for i=1:b.sym2(1)
    l=own(i+b.sym2(2));%边界面对应单元的编号
    A(l,l)=A(l,l)+F_f(i+b.sym2(2)-1)/V(l);
end
for i=1:b.out(1)
    l=own(i+b.out(2));%边界面对应单元的编号
    A(l,l)=A(l,l)+F_f(i+b.out(2)-1)/V(l);
end
end